Modern production equipment and techniques have been developed in the last decade for performing manufacturing operations on production pads and assemblies that are significantly more accurate than the manual manufacturing techniques of the past. The primary goal is to reduce part variation and the secondary goal is to improve the performance and reduce the cost of the manufactured products. A substantial influence on the quality and cost of the manufactured products in the past has been pad variation, the reduction of which reduces the costs of rework and improves fit and function of the product.
One particular version of such a modern manufacturing system known as "virtual tooling", requires accurate information regarding the location and orientation of pads which are to be processed by the automated production machinery. The various types of airplane parts such as shear ties and brackets are picked up by a robot end effector and positioned by the robot at the precise position on a panel at which they are to be fastened. While held in this position, one or more coordination holes are drilled through the pad and the panel to establish the position on the panel where those pads will eventually be fastened. At a later stage in the manufacturing, the panel is hung from a simple fixture and the part is positioned on the panel and fastened thereto by appropriate means such as rivets, bolts and/or sealant.
The location of the pad on the panel is extremely accurate because of the accuracy of the robot, but that accuracy is dependent on an accurate position of the part when it is picked up by the end effector. The end effector must grip the pad at a known position on the pad otherwise there could be significant variation from pad to pad if the end effector were to pick up the pads at different positions on the part. A pad positioning system for presenting the pads to the robot end effector at an accurate and predetermined location and orientation and space was therefore necessary element of this manufacturing system in order to obtain its full potential accuracy.
A part positioning system for use in an airplane factory must be designed ruggedly to withstand continuous rough use over long periods of time without failure or loss of accuracy. It must also be easily and accurately checked for calibration and easily recalibrated if out of adjustment. It should preferably be a simple, uncomplicated construction and be inexpensive to manufacture and use. Finally, it should be fast acting to avoid creating time lags in the production sequence, and be simple and safe to operate.